As a point of comparison, Microsoft ships its OS across a variety of manufacturers and largely keeps it maintained across them (give or take some exceptions like enterprise environments & the like).
Even unlocked Android phones purchased independently of carriers have inconsistent lengths of support, so it doesn’t seem to be entirely a result of carriers, so…What happened here?
Kind poster, I understood about 4% of what you wrote and absorbed 2% (entirely not your fault). Would you say that this explains why Google only supports their Chromebooks for 5 years?
ETA: My question is based on what you wrote here: